I. Field of the Invention
This invention relates to an improved aluminum alloy product for use in making heat exchanger fins and, more particularly, to a fin stock material having high thermal conductivity.
II. Background Art
Aluminum alloys have long been used in the production of heat exchanger fins, e.g. for automotive radiators, condensers, evaporators etc. Traditional heat exchanger fin alloys are designed to give a high strength (UTS) after brazing, a good brazeability (high brazing temperature) and a good sag resistance during brazing. Alloys used for this purpose usually contain a high level of manganese. An example is the aluminum alloy AA3003. The thermal conductivity of such alloys is relatively low. Low thermal conductivity has not been a serious problem in the past because of the significant thickness of the finstock material. If the material is of suitable thickness it can conduct a significant quantity of heat, even if the coefficient of thermal conductivity of the alloy is low. However, in order to make vehicles lighter in weight, there is a demand for thinner finstock material, and this has emphasised the need for improved thermal conductivity. Obviously, thinner gauges tend to impede heat flux as they become thinner.
In addition, fin material properties demanded by the automotive heat exchanger industry require a low (more negative) corrosion potential than the alloys used in the tubes and other parts of the heat exchanger.
The inventors of the present invention have previously found that specific aluminum alloys are particularly suitable for use in finstock material (as disclosed in Applicants' prior unpublished U.S. patent application Ser. No. 09/121,638 filed Jul. 23, 1998, which is assigned to the same assignee as the present application, and which is incorporated herein by reference). These alloys contain Fe, Si, Mn, usually Zn and optionally Ti in particular content ranges. However, an improvement in the thermal conductivity of alloys of this kind would make these alloys even more useful in meeting the stringent demands of the automotive industry, particularly for finstock of thinner gauge.